I'm gonna do failed curses and which of those runes should I buy and which staff should I use? Also... Which place should I cast them, Lessers in karamja volcano or Varrock sewer key room?

Use a water or earth staff. I would use the hobgoblins across from the crafting guild or varrock sewer zombies. Obviously buy bodies and the other rune you need according to which staff you are going to use.

I'm gonna do failed curses and which of those runes should I buy and which staff should I use?

 

 

 

IIRC, you need 1 Body, 2 water, and 3 earth.

 

 

 

So, it would be cheaper to use an Earth staff.

 

 

 

 

 

 

 

Also... Which place should I cast them, Lessers in karamja volcano or Varrock sewer key room?

 

 

 

Almost any place will work.

 

 

 

I like the key room because it's in a multi-combat zone.

 

 

 

That way you will "always" have a target available.

 

 

 

 

 

 

 

Hope this helps